Note: Descriptions are shown in the official language in which they were submitted.
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A TWO-STEP METHOD OF COATING AN ARTICLE FOR SECURITY PRINTING
CROSS-REFERENCE TO RELATED APPLICATIONS
[01] This invention claims priority from US Provisional patent application No.
60/700,994
July 20, 2005, entitled "A Two-Step Method of Coating an Article for Security
Printing".
FIELD OF THE INVENTION
[02] This invention relates generally to a two-step method of making a
security printed image
and more particularly, to a method of forming the image by coating of the
surface of the
substrate with an ink containing alignable flaked material and exposing the
coated surface to a
magnetic or electric field so as to align at least some of the flaked
material, and subsequently re-
coating the substrate with a second printed image over or under of the first
image.
BACKGROUND OF THE INVENTION
[03] This invention relates to the coating of a substrate with an ink or paint
or other similar
medium to form an image exhibiting optically-illusive effects. Many surfaces
painted or printed
with flat platelet-like particles show higher reflectance and brighter colors
than surfaces coated
with a paint or ink containing conventional pigments. Substrates painted or
printed with color-
shifting flaked pigments show change of color when viewed at different angles.
Flaked pigments
may contain a material that is magnetically sensitive, so as to be alignable
or orientable in an
applied magnetic field. Such particles can be manufactured from a combination
of magnetic and
non-magnetic materials and mixed with a paint or ink vehicle in the production
of magnetic
paints or inks. A feature of these products is the ability of the flakes to
become oriented along the
lines of an applied field inside of the layer of liquid paint or ink while
substantially remaining in
this position after drying or curing of the paint or ink vehicle. Relative
orientation of the flake
and its major dimension in respect to the coated surface determines the level
of reflectance or its
direction and, or may determine the chroma of the paint or ink. Alternatively,
dielectric material
may be alignable in an electric field.
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[04] Alignment of magnetic particles along lines of applied magnetic field has
been known for
centuries and is described in basic physics textbooks. Such a description is
found in a book by
Halliday, Resnick, Walker, entitled, Fundamentals of physics. Sixth Edition,
p. 662. It is also
known to align dielectric particles in an electric field, and this form
alignment is applicable to
this invention.
[05]
[06] US Patent 3,853,676 in the name of Graves et al. describes painting of a
substrate with a
film comprising film-forming material and magnetically orientable pigment that
is oriented in
curved configurations and located in close proximity to the film, and that can
be seen by the
naked eye to provide awareness to the viewer of the location of the film.
[07] US Patent 5,079,058 by Tomiyama discloses a patterned film forming a
laminated sheet
comprising a multi-layer construction prepared by successively laminating a
release sheet layer,
a pressure-sensitive adhesive layer, a base sheet layer, and a patterned film
layer, or further
laminating a pigmented print layer. The patterned film layer is prepared by a
process which
comprises coating a fluid coating composition containing a powdery magnetic
material on one
side of the base sheet layer to form a fluid film, and acting a magnetic force
on the powdery
magnetic material contained in the fluid film, in a fluid state, to form a
pattern.
[08] US Patent 5,364,689 in the name of Kashiwagi discloses a method and an
apparatus for
producing of a product having a magnetically formed pattern. The magnetically
formed pattern
becomes visible on the surface of the painted product as the light rays
incident on the paint layer
are reflected or absorbed differently by magnetic particles arranged in a
shape corresponding to
desired pattern. More particularly, Kashiwagi describes how various patterns,
caused by
magnetic alignment of nickel flakes, can be formed on the surface of a wheel
cover.
[09] US Patent 6,808,806 by Phillips in the name of Flex Products Inc.,
discloses methods and
devices for producing images on coated articles. The methods generally include
applying a layer
of magnetizable pigment coating in liquid form on a substrate, with the
magnetizable pigment
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coating containing a plurality of magnetic non-spherical particles or flakes.
A magnetic field is
subsequently applied to selected regions of the pigment coating while the
coating is in liquid
form, with the magnetic field altering the orientation of selected magnetic
particles or flakes.
Finally, the pigment coating is solidified, affixing the reoriented particles
or flakes in a non-
parallel position to the surface of the pigment coating to produce an image
such as a three
dimensional-like image on the surface of the coating. The pigment coating can
contain various
interference or non-interference magnetic particles or flakes, such as
magnetic color shifting
pigments.
[010] US Patent 6,103,361 reveals patterned substrates useful in producing
decorative
cookware formed by coating a base with a mixture of fluoropolymer and magnetic
flakes that
magnetically induce an image in the polymer coating composition. The baked
fluoropolymer
release coating contains magnetizable flakes. A portion of the flakes are
oriented in the plane of
the substrate and a portion of said flakes are magnetically reoriented to form
a pattern in the
coating which is observed in reflected light, the flakes having a longest
dimension which is
greater than the thickness of said coating. The patterned substrate is formed
by applying
magnetic force through the edges of a magnetizable die positioned under a
coated base to induce
an imaging effect or pattern.
[011] A common feature of the above-mentioned prior art references is a
formation of different
kinds of patterns in a painted or printed layer. Most of the patterns exist as
indicia such as
symbols, shapes, signs, or letters; and these patterns replicate the shape of
a magnet often located
beneath the substrate and are formed by shadowing contour lines appearing in
the layer of paint
or ink resulting in particular alignments of magnetic flakes. The desired
pattern becomes visible
on the surface of the painted product as the light rays incident on the paint
layer are reflected or
absorbed differently by the subgroup of magnetic non-spherical particles.
[012] Although these prior art references provide some useful and interesting
optical effects,
there is a need for patterns which have a greater degree of optical
illusivity, and which are more
difficult to counterfeit. United States patent application number 20050106367,
filed December
22, 2004 in the name of Raksha et al. entitled Method and Apparatus for
Orienting Magnetic
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Flakes describes several interesting embodiments which provide optical
illusivity, such as a
"rolling-bar" and a "flip-flop" which may serve as the basis of embodiments of
this invention.
Notwithstanding, there is need to provide different patterns on a single
substrate wherein two
coatings yield images that appear to move independently of one another as the
direction of light
changes or as the image is rotated or tilted.
[013] It is an object of this invention to provide a more complex image having
at least two
distinct features wherein each feature is embodied in a separately applied
coating.
[014] It is an object of this invention to provide a more complex image having
at least two
distinct features wherein each feature is embodied in a separate coating and
wherein the at least
two coatings provide the appearance of two images moving synergistically
together yet
appearing distinct form one another as the image is moved in one direction.
STATEMENT OF THE INVENTION
[015] In accordance with an aspect of the invention there is provided, a
method of coating an
article comprising the steps of:
[016] applying a first magnetic coating to a substrate using a magnetic field
to orient flakes
within the coating along magnetic field lines; and, after the first coating
has cured, subsequently
applying a second magnetic coating over the first coating and using a magnetic
field to orient
flakes within the second coating along magnetic field lines.
[017] In accordance with an aspect of the invention there is further provided,
a method of
coating an article comprising the steps of:
[018] applying a first magnetic coating to a substrate;
[019] using a magnetic field to orient flakes within the coating in dependence
upon the
direction of the magnetic field lines; and,
[020] after the first coating has cured, subsequently applying a second
magnetic coating over
the first coating and using a second magnetic field to orienting flakes within
the second coating
in dependence upon the second magnetic field; and allowing the second magnetic
coating to
cure.
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[021] In accordance with another aspect of the invention there is provided an
image formed of
magnetic particles aligned by a magnetic field, wherein two distinct features
within the image
appear to move simultaneously, and wherein the movement is relative movement,
when the
image is moved or when the light source upon the image is moved.
[022] In accordance with another aspect of the invention there is provided an
image formed of
magnetic particles wherein two distinct features within the image appear to
move, wherein one is
stationary while the other moves, and vice versa, when the image is moved in
two different
directions or when the light source upon the image is moved in two different
directions.
[023] In a broad aspect of this invention, a method of providing an optically
illusive image is
provided comprising the steps of applying a pigment having magnetically
alignable flakes
therein over or under an already formed image, and magnetically aligning the
magnetically
alignable flakes within the pigment and allowing the flakes to cure.
[024] It should be understood, from the above broad aspects of this invention
that preferably
magnetically alignable flakes are used, and a magnetic field is provided to
align the magnetically
alignable flakes; notwithstanding, other forces are fields that can align a
plurality of flakes at a
same time, in a predetermined orientation, are also within the scope of this
application.
[025] More broadly stated, this invention provides a method of forming an
image by applying a
first optical effect coating to a first side of the substrate and using a
magnetic or electric field to
orient flakes within the coating independence upon the field; and,
[026] applying a second optical effect coating over the first coating or over
the second side of
the substrate, wherein effects of both coatings, or combined effects can be
seen from at least one
side of the substrate.
[027] In an alternative embodiment of the invention first and second coatings
include
diffractive flakes, having a surface relief pattern formed therein or thereon,
and flakes in the first
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coating are oriented along their surface relief pattern in a different
orientation than diffractive
flakes in the second coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[028] Exemplary embodiments of the invention will now be described in
accordance with the
drawings in which:
[029] Fig. 1 is a drawing of a gemstone exhibiting aasterism caused by small
needles of rutile
(titanium oxide) exhibiting six rays.
[030] Figs. 2a through 2d depict the steps in the manufacture of an image
having two crossed
rolling bars that appear to move with a change of viewing angle.
[031] Figs. 3a through 3d show a series of steps and images which form a final
image in Fig. 3d
wherein a globe having text therein provides a flip-flop optical effect.
[032] Figs. 4a through 4d depict the steps in the manufacture of a flip-flop
and a rolling bar
created on a same substrate.
[033] Figs. 5a through 5d illustrate the steps in several images of printing
two rolling bars
which appear to move closer together to form a single rolling bar and which
upon tilting the
image appear to separate into two rolling bars.
[034] Figs 6a and 6b illustrate a container with the feature of the rolling
bar of Fig. 5d.
[035] Figs. 7a and 7b micrographs showing an area of an image obtained with a
two steps
printing process, wherein the two micrographs correspond to the same area of
the image.
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DETAILED DESCRIPTION
[036] Orienting of magnetic flakes dispersed in a paint or an ink vehicle
along lines of an
applied magnetic field may produce a plurality of illusive optical effects.
Many of these effects,
described in other patents and patent applications assigned to Flex Products
Inc., have dynamic
animation-like appearance similar to holographic kinograms or a tiger eye
effect in gemstones.
When a graphic image, printed on the surface of a substrate in the presence of
a magnetic field,
is tilted or bent with respect to the light source and to the viewer, the
illusive optical effect
moves toward or out of the viewer, or to the left or to the right.
[037] However, in accordance with this invention it is possible to fabricate
very different and
more complex kinds of optical effects with two-stage printing or painting of
an article with
magnetic ink or paint containing magnetic particles, in the presence of
different magnetic fields.
In the first stage the clear or dyed ink or paint vehicle, mixed with
reflecting or color-shifting or
diffractive or any other platelet-like magnetic pigment of one concentration
(preferably 15-50
weight %), is printed/painted on the surface of an article in any
predetermined graphical pattern,
exposed to the magnetic field to form a predetermined optical effect, and
cured to fix magnetic
flakes in the layer of solid ink/paint vehicle. In the second stage the ink or
paint of lower
concentration (preferably in the range of 0.1 -15wt.%) is printed on the top
of the first printed
image, exposed to the magnetic field, and cured. The ink or paint vehicle for
the second layer is
preferably clear, however may be dyed. Magnetic pigments for the second
printed/painted layer
can be the same as for the first layer or may be different. The pigment size
for the second layer
can be the same or different. The color of the pigment for the second layer
can be the same as
for the first layer or different. The shape and intensity of the field,
applied to the second layer,
can be the same or preferably may be different so that the viewer experiences
two different
effects. The graphical pattern for the second layer can be the same or
different. Combination of
inks or pigments colors may either enhance or depress a particular color in
the final printed
image.
[038] Complex patterns of lines, points, arcs, and other shapes, enhanced with
optically-
illusive effects of current invention, can be utilized in printing process to
make visually
encrypted documents difficult for counterfeiters to reproduce.
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[039] The substrate for the two-step printing in accordance with this
invention can be
transparent or opaque; this is generally determined by the graphics of the
image and the desired
optical effect. In the instance where an opaque substrate is utilized, the
first and second applied
coating layers are printed or painted on a same side of the opaque substrate
with the more
transparent image applied as the second coating over top of the first coating
layer. For
transparent substrates the application for the first and second coatings can
be as described for
opaque substrates, or alternatively and preferably, the first coating layer
can be printed with a
concentrated ink on a first side of the substrate and the second coating layer
can be printed with
diluted ink on opposite side of the substrate. For some purposes, the first
coating layer can be a
printed layer with diluted ink and the layer with concentrated ink can be
printed second.
Observation of a final image can be done through the substrate.
[040] A first example of a printed article in accordance with an embodiment of
this invention,
with two crossing rolling bars produces an optical effect similar to asterism.
United States patent
application numbers 2004/0051297, and 2005/0106367 in the name of Raksha et
al, describe a
single rolling bar and a method for making a rolling bar, wherein the effect
is fontned by a
cylindrical convex or concave reflection of light rays from magnetic particles
dispersed in the ink
or paint vehicle and aligned in the magnetic field.
[041] Asterism in gemstones is caused by dense inclusions of tiny, parallel,
slender fibers in the
mineral which cause the light to reflect a billowy, star-like formation of
concentrated light which
moves around when the mineral is rotated. This is usually caused by small
needles of rutile
(titanium oxide) in the case of ruby and sapphire as exemplified in Fig. 1.
The stars may exhibit
four, six, or more rays.
[042] A flexographic printed image of a box with a four-ray star, or two
rolling bars, is shown
in Figs. 2c and 2d. The image in Fig. 2a of a single rolling bar 202 is
printed in a first step with
ink containing 25wt. % of a green to gold color-shifting pigment on the
surface of clear,
translucent or opaque substrate and the convex rolling bar 202 is formed in
applied magnetic
field.
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[043] The second image shown in Fig. 2b is printed with an ink containing 10
wt. % of the
same green to gold pigment dispersed in a clear ink vehicle (that makes it
translucent) on the top
of the first image 202 and the convex rolling bar 204 is formed in the field
where its direction is
at 900 to the direction of the rolling bar 202 in the first printed image of
Fig. 2a. The resulting
printed image of Fig. 2c shows four rays star. The star moves to the bottom of
the printed image
shown in Fig. 2d, when it is rotated or tilted horizontally with its upper
edge away from the
viewer, or up to the top of the image if it was tilted toward the viewer. By
tilting the image back
and forth in the direction shown in Fig. 2d, both rolling bars appear to
simultaneously move
toward and away from each other. By coating the substrate with two rolling
bars in this manner,
the functionality of each rolling bar of giving the perception of rolling
across the sheet as it is
rotated, is provided so that both bars appear to move synergistically, in
apparently different
directions by even a slight rotation in one direction. In this embodiment it
is not necessary to
move or tilt the sheet in two different directions to view both bars moving. A
single movement in
a single direction gives the perception of two bars moving differently.
[044] Referring now to Fig. 3a, an image of a globe 301, shown was silk-screen
printed with a
thick 30 wt.% ink, containing magenta to gold color-shifting pigment with the
particles averaged
size of 22 microns, and exposed to magnetic field to form the V-shaped flip-
flop optical effect.
The flip-flop effect is described in United States patent applications
2004/0051297, and
2005/0106367, in the name of Raksha et al. In this effect the bottom half
below the equator line
of the globe has bright magenta color and the top side has dark gold color at
normal angle of
observation. Magnetic flakes in the bottom part of the image obtain such
orientation in an
applied magnetic field; these flakes send reflected light right into the eye
of the observer, which
makes them appear bright. In contrast, the particles in the upper part of the
globe send reflected
light in the direction of observer's chest. The color of the flakes at this
observation angle and this
particular particles orientation is gold. When the globe, printed on the
substrate, is tilted with its
upper edge out of the observer the flakes in the bottom part reflect the light
rays in the direction
of the observer's hat that makes them dark gold. Simultaneously, the flakes in
the upper part of
the globe reflect the rays of incident light into the eye of the observer that
visible as bright
magenta. Tilt of the sample in the opposite direction swaps the colors of the
image back.
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[045] The second image 302 "Test Text- shown in Fig. 3b is printed with
diluted 10 wt. % ink
on the top of the globe 301 and exposed to another magnetic field that
produces a roof-shaped
orientation of magnetic particles. An optical effect in the image, printed
with these oriented
particles, has a color "swap" opposite to the color changes of the first
printed image. The
pigment in the second ink is the same magenta to gold as in the first image
but its size is close to
microns. The hue of this pigment has the same value as the larger 22 micron
pigment but its
chroma is lower than the chroma of larger pigment of the first layer that
makes it slightly darker.
At a normal angle of observation, the resulting image 303 in Fig. 3c shows
translucent light
magenta -Text" on a dark gold background and dark gold translucent "Test" on a
bright magenta
globe background. When the print 303 is tilted with its upper edge away from
the observer, as
shown in 304, two parts of the globe and the text interchange or "swap" their
colors. The upper
part of the globe becomes bright magenta with translucent dark gold TEXT and
the bottom part
of the globe becomes dark gold with bright magenta TEST.
[046] The "Text Test" logo 401, shown in Fig.4a, was printed on the top of the
image 402
containing a flip-flop feature described in the abovementioned patents. The
image 402 was
printed with a concentrated ink containing magnetic pigment Al/M/A1 (where Al
is aluminum. M
is any magnetically alignable material). The flip flop can be formed with
either V-shaped or
roof-shaped alignment of magnetic flakes in the solid organic media. At normal
angle of
observation and the V-shape alignment of the particles in the resin, the
bottom part 403 of the
image 402 is bright and the top part 404 is dark. A second image 405 was
printed on the top of
the image 402. In Fig. 4b the image 405 was printed with diluted ink,
containing 5 wt.% of gold
magnetic non-shifting pigment, and placed in the field to form a rolling bar
optical feature. The
rolling bar 406 is formed near top of the image. The ink was cured after
completion of the
particles alignment. The flip flop and the text are highly visible through the
layer of the top coat
in the double-printed image 407 at in Fig. 4d at normal angle of observation.
[047] However, at the tilt of the printed image with its upper edge away from
the observer, the
rolling bar rolls down the printed image 407 and takes a place in the middle
408 of the box
hiding the logo 401 and the flip flop as shown in Fig. 4a. An image 501, shown
in Fig. 5a, was a
flexo-printed on transparent substrate 500 with the ink containing 20 wt.% of
magnetic pigment,
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placed in the field to form the convex rolling bar optical effect 502 and
cured to fix aligned
magnetic particles. Flexo printing or flexographic printing is a machine
printing process that
utilizes rollers or cylinders with a flexible rubber-like surface that prints
with the raised area,
much like surface printing, but with much less ink. In this process the ink
dries quickly and
allows the machine to run at high speed. The finished product has a very
smooth finish with
crisp detail and often resembles rotary screen printing.
[048] In Fig. 5b another image 503 is printed with diluted ink, placed in the
field to form the
concave rolling bar 504 and cured to fix the particles in this position. The
final print 505 shows
at normal angle of observation an image with the single rolling bar effect
506. When the sample
is tilted with its upper edge away from the observer the single rolling bar
506 splits in two rolling
bars 507 and 508 moving in opposite direction. Reversed tilt of the image to
the normal angle
brings the rolling bars 507 and 508 together to make a single optical effect.
Both printed images
may have the same shape, as shown in Fig. 5d, or may have different shapes
[049] Referring now to Figs. 6a and 6b a very attractive image for making of
security labels on
curved surfaces is shown. Pharmaceutical packaging bottles, shown in Fig. 6a
and 6b, are a good
example of utilization of splitting rolling bars. The bottle 601 has a label
602 adhered to its
surface. Security feature 603 with splitting rolling bar described in the
previous example is
printed on the top of the label 602. The feature 603 has a single rolling bar
604 at normal angle
of observation. The bottle has a wide line 605 created by reflection of
incident light from
cylindrical surface of the bottle. However, the rolling bar 604, which also
looks like a reflecting
cylindrical surface, is at 90 to the line 605. Tilt of the bottle 601 with
its top away from the
observer causes a split of the rolling bar 604 in two rolling bars 606 and
607. When the bottle is
tilted back, the rolling bars 606 and 607 collapse in the single rolling bar
604 again.
[050] Turning now to Figs. 7a and 7b, micrograph 7a shows the groove
orientation of the
pigments of a first applied layer of diffractive particles in a carrier using
a magnetic filed
oriented up-down (or vice versa). After the first printed layer was cured, a
second print on top of
the first was applied with a magnetic field oriented left to right (or vice
versa). The camera used.
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to capture the micrograph in Fig. 7b was focused to show the second groove
orientation of the
micro-structured particles. Notice that the loading of the second coating is
lower that the loading
of the first.
[051] It should also be understood that in the subsequent figures and
embodiments shown,
groove oriented flakes can be used in place or along with the other types of
flakes describe
heretofore.
[052] Although the embodiments described heretofore, depict the two-step
application of
coatings to a same or different side of a substrate, less preferably, but
still within the scope of
this invention, is the use a first alignable flake coating on a first
substrate, laminated to a second
substrate having a similar or different printed image or etched image thereon.
For example in a
first step a rolling bar can be printed on a first substrate, which can
subsequently be laminated to
a holographic image, wherein one of the substrates is substantially light
transmissive.
[053] In another less preferred embodiment of this invention two coatings are
applied to
different sides of a substrate, wherein a second of the coatings has a
viscosity which changes
when energy such as light of a predetermined wavelength is applied and the
coating become
fluid; The first coating is a standard coating which can be magnetized and
aligned after being
applied. After the first coating cures and the flakes are permanently aligned,
the second coating
can be made fluid enough to align the flakes, and subsequently cured.
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